Rotor blades for turbomachines, such as turbines and compressors, and also their mountings, are widely known from the prior art. For example, it is known that rotor blades have a root section with an essentially dovetail-like appearance, wherein the two mutually opposite sidewalls of the blade root diverge rectilinearly from the platform in the direction towards a blade root underside. For fastening, a rotor, which carries these rotor blades, in most cases has a shaft collar or a correspondingly formed rotor disk, on the generated surface of which retaining grooves—with a contour corresponding to the blade root—extend in the axial direction. The rotor blades can be inserted by their dovetail-shaped blade root into the corresponding retaining grooves and, on account of the dovetail connection created in this way, are securely retained against disengagement in the radial direction during rotation of the rotor.
For example, such a blade fastening is known from DE 41 08 930 A1. In order to achieve the service life limit values with regard to fatigue with low and high stress cycle numbers in this case, it is provided that the dovetail hook-in fastening is a section of a helix. Furthermore, a rectilinear—but inclined in relation to the radial direction of the turbine rotor—dovetail root of a rotor blade is known from EP 0 502 660 A1. This arrangement, however, is provided only for non-metallic blades.
In addition, it is known from the prior art to fasten rotor blades on rotor disks by means of so-called fir tree toothing. To this end, both the blade root of a rotor blade and the retaining groove, which is formed correspondingly to it, have contours with an appearance corresponding to a fir tree. The undercuts and projections which are thereby provided and inter-engage can give rise to stresses in the material of the rotor disk or of the rotor blade root in the event of high centrifugal force load on account of the rotor rotating at high speed, which can lead to fatigue phenomena.